In thin layer chromatography, what causes separation

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Principle of thin layer chromatography (TLC)

"... easy for beginners and tricky for professionals ..."

Thin layer chromatography ( engl. thin layer chromatography, TLC) is a liquid chromatography process that takes place in an open system. The environment plays an important role for the sorbent layer (stationary phase, e.g. water from the air accumulates at the active centers of the surface).

In the TLC, the flow agent is moved through the sorbent layer solely by capillary forces and transports the substances in the analyte mixture with it. In contrast to column chromatography, the flow rate cannot be easily influenced here. With this analytical method, reproducible work often requires running a standard, since a number of factors influence the separation and are difficult to control.

The result of the TLC is an internal chromatogram, i.e. the substances are detected while they are in the separation bed - they do not leave the separation bed. It contains qualitative statements (position of the substance stain) and quantitative information (area of ​​the substance stain), which can be deciphered primarily through repeated detection (methods with different sensitivity and selectivity). The chromatograms are usually evaluated visually. In comparison to column chromatography, in which a period of time is measured at the end of the chromatographic bed, in TLC the path difference in the separating bed is decisive.

TLC is the most flexible chromatographic method in modern analysis. It has a significantly more favorable price-performance ratio (a lot of data in a short time with a low risk) with an extraordinary selectivity of the separation.

Thin-layer chromatography basically consists of three work steps: the application of the samples, the development of the chromatogram in the chamber and the qualitative or quantitative detection. However, the respective separation problem can also make further work steps necessary: